Pins are used in many applications for connecting electrical conductors to PCBs, the pins being soldered to the PCB. In soldering, a flux is used, which wets the pin and creeps along its surface. In such cases it is a known problem that during soldering the flux can creep to the upper part of the pin where there are the connected electrical conductors. The flux can there act chemically on an integrated circuit which is connected via the pin, for example, or constitute a contact resistance between the pin and a gliding contact thrust on to it. In order to prevent the flux from creeping along the pin it has been proposed to provide a tight closure round the pin, e.g. as described in the German patent application DE 3414343. In this publication there is described an insulating casing with pins for electrical connection, these pins being fixed in holes in the walls of the casing. Each pin has a transverse protuberance which is pressed into a corresponding hole in the casing. However, it has been found difficult to achieve a completely tight closure in this way, and it has been proposed to further seal the closure with the aid of glue or lacquer. A completely sealed closure has not been able to be provided with the aid of these sealing means either, and the flux has crept past the closure by capillary action.